Low-Coordinate Magnesium Sulfide and Selenide Complexes.

The reactions of [{(NacNac)Mg}] (nacnac = HC(iPrCNDip)) with PhP═O at 100 °C afforded the phosphinate complex [(NacNac)Mg(OPPh)(OPPh)] . Reactions of with PhP═E (E = S, Se) proceeded rapidly at room temperature to low-coordinate chalcogenide complexes [{(NacNac)Mg}(μ-S)] and [{(NacNac)Mg}(μ-Se)] , respectively. Similarly, reactions of NHC═S ((MeCNR)C═S with R = Me, Et, or Pr) with afforded NHC adducts of magnesium sulfide complexes, [{(NacNac)Mg(NHC)}(μ-S){Mg(NacNac)}] , that could alternatively be obtained by adding the appropriate NHC to sulfide complex .

Umpolung of an Aliphatic Ketone to a Magnesium Ketone-1,2-diide Complex with Vicinal Dianionic Charge.

The new β-diketimine nacnacH, HC(iPrCNDip) H, Dip=2,6-iPr -C H , was converted to the magnesium(I) complex [{( nacnac)Mg} ] and reaction with 2-adamantanone (OAd) afforded the ketone-1,2-diide complex [{( nacnac)Mg} (μ-OAd)]. The complex contains the first stable dianion of an aliphatic ketone with an electropositive metal and shows an OAd unit with long C-O bond and pyramidal carbon centre. DFT studies reveal an anionic charge on both neighbouring C and O atoms.

Normal and abnormal NHC coordination in cationic hydride iodide complexes of aluminium.

The mixed N-heterocyclic carbene (NHC) complexes NHCAlHxI3-x, where NHC is IDip or IMes ((HCNAr)2C:, Ar = 2,6-iPr2C6H3 = Dip (IDip); or 2,4,6-Me3C6H2 = Mes (IMes)), x = 1 or 2, were either prepared from NHCAlH3 and NHCAlI3 or by halogenation of NHCAlH3 with MeI. Reaction of [(IDip)AlHxI3-x], with x = 0-3, with another equivalent of IDip afforded either fluxional equilibria in benzene solution for x = 0, no reaction for x = 3, or the new mixed normal-abnormal NHC-coordinated ionic complexes [(IDip)AlH2(aIDip)]I (9) and [(IDip)AlHI(aIDip)]I (10), where aIDip is the abnormal IDip carbene tautomer bonded through its 4-position. The molecular structures of 9 and 10 were determined and show slightly shorter Al-C(aIDip) than Al-C(IDip) distances.

A study of tumor motion management in the conformal radiotherapy of lung cancer.

Purpose: To assess the benefit derived from the reduction of planning target volumes (PTVs) afforded by tumor motion management in treatment planning for lung cancer.

Methods: We use a simple formula that combines measurements of tumor motion and set-up error for 7 patients to determine PTVs based on the following scenarios: standard uniform 15 mm margin, individualized PTVs (no gating), spirometry-based gating, and active breath-control (ABC). We compare the percent volumes of lung receiving at least 20 Gy (V20) for a standard prescription, and the maximum tolerated doses (MTDs) at fixed V20.

A deformable-model approach to semi-automatic segmentation of CT images demonstrated by application to the spinal canal.

Because of the importance of accurately defining the target in radiation treatment planning, we have developed a deformable-template algorithm for the semi-automatic delineation of normal tissue structures on computed tomography (CT) images. We illustrate the method by applying it to the spinal canal. Segmentation is performed in three steps: (a) partial delineation of the anatomic structure is obtained by wavelet-based edge detection; (b) a deformable-model template is fitted to the edge set by chamfer matching; and (c) the template is relaxed away from its original shape into its final position.

Assessment of consistency in contouring of normal-tissue anatomic structures.

The purpose of this work is to estimate the uncertainty in the manual contouring of normal anatomical structures. The heart, esophagus, and spinal cord were contoured manually on six sets of computed tomography images by six dosimetrists whose experience ranged from 1 year to over 15 years. To determine the differences between inter- and intraobserver variations, each data set was contoured by one of the dosimetrists five times and once each by the five other dosimetrists.